1. Field of the Invention
Embodiments of the present disclosure relate to cementitious composite materials incorporating reinforcement fibers with improved properties developed primarily for use in the building and construction industry.
2. Description of the Related Art
Fiber reinforced cementitious composite materials have been widely used in building construction. Cellulose fibers, in particular, have been used to reinforce various fiber cement building products because they impart favorable properties to the building product. Moreover, cellulose fibers have a unique microstructure with unique physical and mechanical properties that are suitable for the Hatschek process, the preferred commercial process for manufacturing fiber cement sheets and panels. For example, the micro-fibrils in cellulose fibers help to build an effective filtration system to catch the fine particles in the fiber cement slurry to form a thin fiber-particle film during the Hatschek process. The micro-fibrils also branch out with the branches functioning as anchors in the cured fiber cement composite thereby enhancing the bonding at the interface between the fibers and cementitious matrix.
However, there are also disadvantages associated with using cellulose fibers to reinforce cementitious building products. For example, the chemical composition and large surface area of the micro-fibril structure of the cellulose fibers render the fibers highly hydrophilic. The hydrophilic nature of cellulose fibers can increase water absorption of the fiber cement composite, which can result in some performance issues. Furthermore, cellulose fibers are generally more water sensitive and less alkali resistant. Therefore they can experience progressive degradation over time.
While synthetic fibers have been used to reinforce cementitious composite materials, prior art products reinforced with synthetic fibers not only require a much longer manufacturing cycle but also have less than desirable mechanical properties as compared to products reinforced with cellulose fibers. For example, fiber cement composites reinforced with synthetic fibers have been typically limited to the air cure process because synthetic fibers tend to disintegrate at high temperature conditions of the autoclave process that is commonly used for curing cellulose fiber reinforced cement composites. The air cure process takes much longer, normally 28 days, as compared to the autoclave cure process, which usually takes less than 3 days. Replacement of cellulose fibers with synthetic fibers can also result in lower flexural strength of the fiber cement composite due to the lower fiber-matrix interface bonding. Moreover, non-cellulose fibers can create added difficulties in manufacturing using the Hatschek process. Accordingly, there is a need for improved reinforcement fibers that can impart desirable mechanical properties to cementitious composites and are also compatible with the Hatschek process and autoclave curing.